McCausland Avenue UPRR Bridge (St. Louis, Missouri)Built 1958; replaced 1992 by a new bridge on a new alignment of the railroadLost steel stringer bridge over McCausland Avenue on the Union Pacific Railroad, just south of Manchester Avenue in St. LouisReplaced by new bridge

McKnight Road Bridge (Carver County, Minnesota)Built 1913 to cross dual tracks of the CMStP&P, closed 2009Pony/through plate girder bridge over TC&W RR on McKnight RoadIntact but closed to all traffic, scheduled to be replaced in the coming years

MCRM - Baraboo River Bridge (Sauk County, Wisconsin)Built in 1903Plate girder bridge over Baraboo River on Mid Continent Railroad MuseumOut of service

MDS - Chickasaway River Bridge (Clarke County, Mississippi)Built 1906 by the Wisconsin Bridge & Iron Co.Warren through truss bridge over Chickasaway River on the Meridian Southern Railway (formerly Mobile and Ohio RR)Open to traffic

MEC - Passumpsic River Bridge (Caledonia County, Vermont)Built 1928 by the American Bridge Co.; Abandoned 1983Warren through truss bridge over Passumpsic River on former Maine Central Railroad in St. JohnsburyDerelict/abandoned

MEC - Sandy River Bridge (Franklin County, Maine)Removed sometime after 1994Lost Through truss bridge over Sandy River on MEC Farmington BranchDestroyed by flooding

Merchants Bridge (St. Louis, Missouri)Completed in May 1890; approaches rebuilt in 2005Three-span through truss railroad bridge over the Mississippi River between St. Louis and Venice, Illinois on Terminal Railroad AssosiationOpen to two tracks of railroad traffic. Only one train is allowed to cross the bridge at a time, due to its age.

Meridian Bridge (Yankton County, South Dakota)Built 1924; rehabilitated 1953; bypassed by Discovery Bridge in 2008Vertical-lift through truss bridge over the Missouri River on US 81 at YanktonClosed to traffic

MERR - Carlton Lift Bridge (Sagadahoc County, Maine)Built 1927 by McClintic-Marshall Co. ; rehabilitated 1976; Bypassed by new highway bridge in 2000Warren through/deck truss lift Bridge over Kennebec River on Maine Eastern Railroad and former US 1 in BathOpen to railroad traffic only